16700A: No display on external monitor

I have a 16700A with a screen and keyboard attached. The bootrom winds up and does the initial tests, and displays the following on the serial port:

"Firmware Version 1.0

Duplex Console IO Dependent Code (IODC) revision 1

Memory Test/Initialization Completed

"

But what it does not display prior to trying to do anything further is the message that reads:

"To select a new Graphics Monitor Type press the [TAB] key now, otherwise EXIT byentering any other key (or will time out in 15 seconds)..."

"

The video system is putting out synch signals that match the configured mode for the monitor, but nothing is visible on the monitor. The system also appears unresponsive to the keyboard.Both the keyboard and monitor are OK.

Does anyone have some thoughts on what might cause this particular set of behaviour? Or how to find out what the problem is.

I realise that unless I am lucky I will need to change a board, but at least knowing the likely problem area will help a lot.

ThanksDave

PS It won't boot HP_UX in headless mode as the HDD is toast - I got a new disk drive today and am waiting for the Re-Ignite CD to be sent to me.

It's quite possible that something happened to cause the monitor to be "de-configured". The message about changing the monitor comes out only on the monitor, IIRC. If you press the [TAB] key at the right time, the monitor input will cycle through the 23 (or so) different monitor modes, at about 3 seconds each. When you see something on the monitor, you can press the [ENTER] key, then [Y] to choose that mode.

Depending on your specific monitor HW, it may not react fast enough to actually display anything, so I used to watch the LED on the monitor. It would usually react before anything was on the screen, so when it turned green, I would press [ENTER]. There a way to get a list of modes from the Boot manager, once you have something on the screen, and set it, but I've forgotten how to do that.

It looks as if its not recognising the KBD. When I checked initially, both Pin 1 (data) and Pin5 (clock) were low.

I traced the signals for pin 1 and pin 5 of the keyboard connector, which leave the board on the 50 pin connector J7 going to J14 on the interface board. Pin 30 carries the KBD pin 1 signal and Pin 32 the pin 5 signal.

The signal then goes directly to J4 in the interface board which connects to J2 on the CPU board. Pin 91 carries the KBD pin 1 signal, and pin 90 the KBD pin 5 signal.

This then goes to J16 which connects to the PCI board J7. Pin 3 carries the KBD pin 5 signal and pin 4 the KBD pin 1 signal. As far as I can tell these pins connect to nothing further on the PCI board.

Returning to the CPU board the signals carry on to some 51 ohm resistors which in turn connect to a monster HP custom IC - U31. Please see: <http://www.perdrix.co.uk/pix/16700A_KBD_test_points.jpg>.

Looking at this carefully I found that there was a small solder bridge (solder splatter perhaps) between the fourth and fifth pins counting from the top right which was shorting them together. I cleaned this out and soldered a couple of test wires to the points where the signals from the KBD emerge. The one on the left is KBD pin 5, and that on the right is KBD pin1.

Now things look somewhat different. Pin 1 jumps to +5V on power up, and as the boot proceeds there is clearly some communication taking place with the keyboard during the boot process. Whether it is "good" comms or broken I'm not sure - it's not turning on the NUM-LOCK light as the initial phase of the boot completes, nor is the "Press TAB key" message appearing (maybe because a valid mode has been selected already). No boot messages are presented on the monitor (they are of course there on the serial port).

1) The was a solder bridge (only visible under a microscope) on two of the leads of the LASI chip, which was dragging the keyboard clock line to ground.

2) The 16700A is very fussy about what keyboards it accepts - it refuses to play if an REAL IBM PS/2 keyboard is connected, and also would not work with one of my Dell keyboards. Luckily I found an "A. N. Other" brand keyboard which it would tolerate.